LO: TO UNDERSTAND HOW TEXT IS REPRESENTED IN A COMPUTER SYSTEM

ascii

We now know that all data must be converted into 1s and 0s (ON or OFF) for your computer to understand. This means that when a key on your keyboard is pressed it must be converted into binary. The keyboards that we use on a daily basis use a character set called ASCII to do this. ASCII assigns each character on your keyboard a binary number. This is shown in the tables below….

ASCII CHARACTER SET

ASCII%20Table%201

ASCII%20Table%202

Lesson Tasks

ASCII Tasks

Copy the code below in to a new Python file.

# Lets the user select 's' to encode a message for sending
# Or 'r' to translate a received message
choice = input("Enter 's' for Send of 'r' for Receive: ")
# Encoding a message for sending
if choice == "s":
    message = input("Enter your message: ")
    binary_message = ""
    # Loops through the message character by character
    for i in message:
        # Converts each letter into it's denary ASCII code
        ascii_denary = ord(i)
        # Converts the denary ASCII code to 8-bit binary
        # and joins it all to gether as one long string
        binary_message += bin(ascii_denary)[2:].zfill(8)
    # Outputs the binary converted message
    print(binary_message)

# Decoding a received message
elif choice == "r":
    binary_message = input("Enter your message: ")
    message = ""
    # Loops through the binary message in steps of 8
    for i in range(0,len(binary_message),8):
        # Picks out binary blocks of 8
        binary = binary_message[i:i+8]
      # Converts them into base-2 (denary)
        number = int(binary, 2)
        # Converts the denary ASCII code into characters
        # and joins it all together as one long string
        message += chr(number)
    # Outputs the translated message
    print(message)

else:
    exit()

Save the program in to your Programming folder, call it ASCII-Binary_Converter.  Run the program, click on ‘s’ at the start to encode a message.  Email the binary output to a friend who should then run the program again but this time select ‘r’ to translate the binary back to characters.  Keep it clean!

Extension:  Take a look at the code, see if you can work out how it works.  Use the comments for guidance.